"Once you've protected a place that can host a grizzly bear or a wolf, you have protected a place that can host all kinds of smaller, less well-known species that are part of the broader ecosystem and that will produce the kinds of things like clean air and clean water that we all depend on."

When the Endangered Species Act became law in 1973 it came too late for many areas of the country, which had already lost much of their wildlife. Not so in Yellowstone and the Northern Rockies. It was wild enough there to allow the law to work. "All the success was made possible by the Endangered Species Act," says Tim Preso, head of Earthjustice's Northern Rockies regional office.

Preso grew up in eastern Oregon and spent four and a half years as an environmental reporter in Bend, Oregon. This was during the time the spotted owl was big news in the Northwest. Tim found himself writing about the lawsuits that were gaining protection for the owls and thought that it might be better to do something about environmental issues than simply write about them. He went to law school and eventually joined the staff of Earthjustice in 2000.

His office is, and for decades has been, active in efforts to protect wildlife in the region: wolves, grizzly bears, wolverines, bison and many other species. A majority of their efforts are based on the Endangered Species Act.

It's been a rocky road. Multiple attempts have been launched to strip legal protection from the bears, but Earthjustice litigation reinstated "threatened" status under the ESA for the species.

The situation with the wolves is a bit different. After Canadian wolves were released in Yellowstone in the 1990s, their population thrived, to the great benefit of the park and its wildlife. This provoked a backlash by wolf-haters in the region. Congress got involved and assigned management to Montana, Idaho and Wyoming. The first two states are busy enacting the most anti-wolf measures they can think of. Earthjustice is still in court challenging Wyoming's draconian wolf plan. Wolf hunts are being conducted in all three states. If Montana and Idaho continue down the road they're on, Preso and his colleagues may try to get the wolves returned to the protection of the ESA.

Grizzly bear and cubs in Yellowstone National Park. National Park Service

Another of the species Preso has worked to save for years is the wolverine, an elusive and rare species of weasel. Years of litigation finally got the Fish and Wildlife Service to propose listing the species.

And though bison are not on the endangered species list, Preso's office has expended great effort on behalf of the bison, which were routinely slaughtered in large numbers as they left Yellowstone in search of food in winter. An agreement was reached to transfer a slice of the Yellowstone population of bison to the Fort Peck Reservation in Montana, part of their historical range.

The battles may never end, but so far there's much to be proud of: The bears retain ESA protection and Earthjustice efforts have stopped clear-cutting and the building of roads in grizzly habitat. Despite efforts of wolf-haters, Preso insists that "the wolves are here to stay."